As a medical syringe (hereinafter referred to as merely “syringe”), a pre-filled type syringe that is provided in a state that a medical solution is preliminarily filled in the syringe, a filled-in use type syringe that is provided in a state that a medical solution is not filled in the syringe, the medical solution being filled at the time of use, and the like are used.
With regard to the filled-in use type syringe as mentioned above, a method that parts such as a syringe barrel, a piston, a plunger rod are provided in a state separated from each other and are assembled at the time of use may be considered. However, the above-mentioned method not only increases a burden of nurses who are busy, but also raises a concern about hygiene issue such as a fear that the syringe is contaminated by microorganisms at the assembling work. Consequently, it is common that the filled-in use type syringe is provided as a pre-assembled type syringe in which parts such as a syringe barrel, a piston, a plunger rod are preliminarily assembled. The pre-assembled type syringe is included in a well-known, commonly used art, thus there is no prior art literature information to be described.